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Updated: Mar 31, 2026
Generation and Characterization of Human Induced Pluripotent Stem Cell-derived Astrocytes Lacking Fragile X Messenger Ribonucleoprotein
Published on: June 6, 2025
Persistent astrocyte activation in the fragile X mouse cerebellum
Laura K K Pacey1, Sihui Guan1, Sujeenthar Tharmalingam1
1Department of Pharmaceutical Sciences Leslie Dan Faculty of Pharmacy University of Toronto 144 College Street Toronto Ontario Canada M5S 3M2.
Background:
Fragile X Syndrome, the most common single gene cause of autism, results from loss of the RNA-binding protein FMRP. Although FMRP is highly expressed in neurons, it has also recently been identified in glia. It has been postulated that in the absence of FMRP, abnormal function of non-neuronal cells may contribute to the pathogenesis of the disorder. We previously demonstrated reduced numbers of oligodendrocyte precursor cells and delayed myelination in the cerebellum of fragile X (Fmr1) knockout mice.
Methods:
We used quantitative western blotting and immunocytochemistry to examine the status of astrocytes and microglia in the cerebellum of Fmr1 mice during development and in adulthood.
Results:
We report increased expression of the astrocyte marker GFAP in the cerebellum of Fmr1 mice starting in the second postnatal week and persisting in to adulthood. At 2 weeks postnatal, expression of Tumor Necrosis Factor Receptor 2 (TNFR2) and Leukemia Inhibitory Factor (LIF) were elevated in the Fmr1 KO cerebellum. In adults, expression of TNFR2 and the glial marker S100β were also elevated in Fmr1 knockouts, but LIF expression was not different from wild-type mice. We found no evidence of microglial activation or neuroinflammation at any age examined.
Conclusions:
These findings demonstrate an atypical pattern of astrogliosis in the absence of microglial activation in Fmr1 knockout mouse cerebellum. Enhanced TNFR2 and LIF expression in young mice suggests that changes in the expression of astrocytic proteins may be an attempt to compensate for delayed myelination in the developing cerebellum of Fmr1 mice.
Insights
Fragile X Syndrome (FXS) involves loss of FMRP protein. In FXS mice, astrocytes show altered protein expression, suggesting a role in delayed myelination, independent of neuroinflammation.
Area of Science:
- Neuroscience
- Genetics
- Cell Biology
Background:
- Fragile X Syndrome (FXS), a leading single-gene cause of autism, stems from the loss of the Fragile X mental retardation protein (FMRP).
- While FMRP is primarily neuronal, its presence in glia suggests non-neuronal cells may influence FXS pathogenesis.
- Previous studies noted reduced oligodendrocyte precursor cells and delayed myelination in the cerebellum of Fmr1 knockout mice.
Purpose of the Study:
- To investigate the status of astrocytes and microglia in the cerebellum of Fmr1 knockout mice during development and adulthood.
- To understand the role of glial cells in the neuropathology of Fragile X Syndrome.
Main Methods:
- Quantitative western blotting and immunocytochemistry were employed.
- Cerebellar tissues from Fmr1 knockout and wild-type mice were analyzed at various developmental and adult stages.
Main Results:
- Increased glial fibrillary acidic protein (GFAP) expression, an astrocyte marker, was observed in Fmr1 knockout mice from the second postnatal week into adulthood.
- Elevated levels of Tumor Necrosis Factor Receptor 2 (TNFR2) and Leukemia Inhibitory Factor (LIF) were detected in young Fmr1 knockout mice.
- Adult Fmr1 knockouts showed increased TNFR2 and S100β (glial marker) but normal LIF levels compared to wild-type.
- No evidence of microglial activation or neuroinflammation was found at any age.
Conclusions:
- Fmr1 knockout mice exhibit atypical astrogliosis without microglial activation in the cerebellum.
- Enhanced TNFR2 and LIF expression in young Fmr1 knockout mice may represent a compensatory mechanism for delayed myelination.
- These findings highlight the contribution of glial cell alterations to the cerebellar phenotype in Fragile X Syndrome.
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